doc: use a linked reference rather than a GitHub reference.

Instead of sending the user out of the documentation site to GitHub
to read the testing instructions, link to the generated page for the
documentation.

Signed-off-by: Diego Elio Pettenò <flameeyes@meta.com>

samples/sample_definition_and_criteria.rst

@@ -24,12 +24,12 @@ Sample Criteria
 
   * If a sample can provide output that can be verified, then output should be evaluated against
     expected value to have some level of testing for the sample itself.
-    Refer to :zephyr_file:`doc/develop/test/twister.rst` for more details.
+    Refer to :ref:`twister_script` for more details.
   * Samples are optional.
 
 2. Twister should be able to build every sample.
 ++++++++++++++++++++++++++++++++++++++++++++++++
-  * Every sample must have a YAML file. Reference: :zephyr_file:`doc/develop/test/twister.rst`.
+  * Every sample must have a YAML file. Reference: :ref:`twister_script`.
 
     **For example:**
 
@@ -62,7 +62,7 @@ Sample Criteria
 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
   * Minimize the use of ``platform_allow`` and architecture filters as it limits the scope
     of testing to the mentioned platforms and architectures.
-    Reference: :zephyr_file:`doc/develop/test/twister.rst`
+    Reference: :ref:`twister_script`
   * Make use of ``integration_platforms`` to limit the scope when there are timing or
     resource constraints.
   * Make the sample as generic as possible. Avoid making a sample platform specific unless it is